No search was conducted on the method of forming a high performance reflective film on a glass sheet in the U.S. Patent and Trademark Office or in any other search facility.
We are aware of prior work, which has been done by our associates at Ford Motor Company, developing powdered, organic based, metal containing glass coating compositions which are heat pyrolyzable to form a film on a heated glass sheet.
In U.S. application Ser. No. 434,642, now U.S. Pat. No. 4,393,098, filed Sept. 20, 1982, as a continuation-in-part of earlier filed U.S. application Ser. No. 325,891, filed Nov. 30, 1981, now abandoned, our associates disclosed a method of placing a metal oxide film on a surface of a heated glass sheet. In that particular application, a powder was disclosed which was made up of 76% by weight cobalt acetylacetonate, 12% by weight iron acetylacetonate, and 12% by weight chromium acetylacetonate. The patent application goes on to describe, in detail, the manner in which that powder is applied to a heated glass surface in order to develop a film on the glass sheet.
In U.S. application Ser. No. 425,195, now U.S. Pat. No. 4,397,671 filed July 29, 1982, also assigned to Ford Motor Company, our associates disclosed still another process for developing a coating film on a heated glass sheet. In this application our associates disclosed a method of preparing a special powder spray composition which comprised a plurality of hollow, generally spherical particles which are used as the spray composition for spraying against a heated glass sheet. In this disclosure the particular composition disclosed for developing the spherical particles was an initial powder mixture which consisted of about 70% by weight cobalt acetylacetonate, 18% by weight iron acetylacetonate, and 12% by weight chromium acetylacetonate.
We are also aware that Ford Motor Company uses organo metallic materials dissolved in a suitable solvent such as methylene chloride for application to the surface of a heated glass sheet in order to develop a film on the glass sheet. In the solution sprays used by Ford Motor Company there is approximately, by weight percent, 12.5% by weight solids and 87.5% by weight of solvent. The solid composition is generally made up of cobalt acetylacetonate in a range from 66.5-68.5% by weight, chromium acetylacetonate 12-14% by weight, with the balance being iron acetylacetonate in a range generally from 18.5-20.5% by weight.
The one thing that did not result from the application of the coating compositions set forth above is a true high performance reflective glass film on a glass sheet. By a high performance reflective glass film we mean one that has a "shading coefficient" of 0.40 or less. A shading coefficient is defined in the architectural glass business as the ratio of the solar heat gain for any given glass to the solar heat gain under the same conditions for 1/8 inch clear glass.
It is well known that architects today use vast amounts of glass for enclosing large buildings such as commercial office buildings and hotels. It is essential that glass used in such structures generally have a high performance reflective film thereon which is effective in reflecting solar energy so that reflected energy does not enter the building's interior. This is particularly true in areas such as the "sun belt" areas of the United States.
It is therefore a principal object of the method of this invention to provide a method for forming a high performance reflective film on a glass sheet, the high performance reflective film having a shading coefficient of 0.40 or less (based upon a 1/8 inch thick clear glass sample having a shading coefficient of 1.0).